ERIC IDLE has said that he set out to be very funny and very silly when he and the composer John Du Prez “lovingly ripped off” Monty Python and the Holy Grail, transforming a cult movie into a stage musical; and you’d have to be a dead parrot not to agree that he has fulfilled both aims. Indeed, this live Nightingale replayed the original film last weekend and found it a bit sluggish beside a show which, though slicker and maybe blander, kept him in infantile bliss from the moment Tim Curry’s gloriously plummy, blimpish Arthur trotted onstage with a serf making horse-noises with coconut shells.

Apart from the scene in which nymphomaniacs attempt the mass rape of one of Camelot’s grail-sleuths, everything familiar is retained. The French defy the English knights by throwing a cow off their ramparts and sneering “I fart in your general direction”. The killer bunny puts in an appearance, as do the murderously squeaking Knights Who Say Ni, the walled-up damsel who turns out to be a lad called Herbert, and the tattered peasants who collect plague-victims — this time with an oldster lustily chanting “I’m not dead yet” and doing a Highland fling as he resists being carted to a mass grave.

The songs are, of course, the prime innovation. Idle has imported his fake-optimistic Always Look on the Bright Side of Life (”when you’re chewing on life’s gristle, don’t grumble, give a whistle”) from Life of Brian and given it to knights twirling orange parasols. And Du Prez sends up just about everything: martial, gospel, torch-song, cheerleader choruses, smoochy-sweet, scat, jaunty tap, West Side Story, Sondheim’s Company, and (hilariously put over by Hannah Waddingham’s brilliant Lady of the Lake) power ballads and every variety of Andrew Lloyd Webber.

Gradually Mike Nichols’s production becomes less a satire on chivalry, war and things medieval and more a parody of Broadway musicals, complete with sexy girls dancing in a Camelot that doubles as a casino. But this brings its own problems. The Knights Who Say Ni don’t just require Arthur to bring them a shrubbery, as in the film.

They order him to take his show to the West End — and he does so, self-referentially ending up in the Palace Theatre and discovering the grail under a seat.

But London is less narcissistically obsessed with its theatre than New York, and the idea worked better when Arthur’s destination was the place where the musical was first staged: Broadway. Moreover, the attendant notion, which is that no show can succeed without Jews, means a lot less here than there. But Idle presumably didn’t want to lose his Fiddler on the Roof pastiche, so the episode remains more or less uncut, adding to the second half’s rather scattered, frantic feel.

Never mind. It’s hard to resist a show which, with jokes about Tom Goodman-Hill’s gay Lancelot and his predilection for Darren Southworth’s demure Herbert adding to the fun, remains cheerfully mischievous throughout. It’s hard to resist the transformation of Christopher Sieber’s anarcho-syndicalist shop steward into the hair-tossing nob, Sir Dennis Galahad, or Curry’s Arthur when he launches into the sob-song in which, ignoring his serf and a dozen knights, laments the agony of being all, all alone.

Silly? Very. Funny? You bet.

Box office: 0870-895 5579

Editor's choice

• The 100 Best Films of the Decade
• 70 facts you didn't know about Marvel
• The 50 Biggest Movies Of 2010